1. Field of the Invention
The present invention generally relates to a light source apparatus, and more particularly, to a surface light source apparatus with dual-side emitting light to produce desired light.
2. Description of Related Art
A light source apparatus is widely used in our daily life. A traditional light source apparatus, for example, a bulb, produces visual light through the filament thereof with a high temperature after turning on. The bulb light source is counted as spot-like light source. After the spot-like light source, a tube-like light source was developed as well. Thereafter, through long time developments and modifications, a surface light source apparatus was lunched, which now is broadly used in, for example, flat displays.
A surface light source works based on various mechanisms. FIG. 1 is a cross-sectional diagram showing a mechanism of a conventional surface light source apparatus. Referring to FIG. 1, the light-emitting is produced by such a mechanism: connecting a power supply 106 to two electrode structures 100 and 102; producing an electric field under an operation voltage by the electrode structures 100 and 102 so as to establish gas discharge, termed as plasma discharge as well; ionizing the gas 104 so that the electrons 110 in the conductive gas likely hit the gas molecules to cause an electron transition with the ultraviolet emission; impacting the fluorescent layers 108a, 108b and 108c corresponding to different colors on the electrode structure 102 by the emitted ultraviolet (UV); finally emitting visual light 112 after the fluorescent layers 108a, 108b and 108c (for example, a red fluorescent layer, a green fluorescent layer and a blue fluorescent layer) absorb the UV. The electrode structure 100 herein is a light-emitting surface; therefore, the electrode structure 100 usually is a transparent material, for example, one composed of glass substrate and an ITO (indium tin oxide) transparent conductive layer.
FIG. 2 is a cross-sectional diagram showing another mechanism of a conventional surface light source apparatus. Referring to FIG. 2, a cathode structure layer 122 is disposed on a glass substrate 120, a plurality of conical conductors 124 are disposed on the cathode structure layer 122, a gate layer 126 is disposed on the conical conductors 124 and a plurality of holes are made on the gate layer 126 and the holes are corresponding to the conical conductors 124. An anode structure layer 128 with a transparent anode layer is disposed on another glass substrate. In addition, a fluorescent layer 130 is disposed on the anode structure layer 128, and a high electric field between the cathode and the anode makes electrons 132 escaped from the tips of the conical conductors 124. Thereafter, the electrons 132 are accelerated by the electric field and then impact the fluorescent layer 130 so as to make the fluorescent layer 130 emits light.
The above-mentioned two conventional light-emitting mechanisms respectively have advantages and disadvantages of their own. The mechanism based on gas discharge has advantages of structure simplicity and easily light-emitting, but to emit light, it needs to produce plasma first and the light-emitting mechanism is based on secondary energy conversion, which consumes a lot of electrical power. In contrast, the mechanism based on field emission, the corresponding light source is counted as a cold light source similar to a cathode ray tube (CRT), where electrons in high speed within vacuum directly impact fluorescence powder to emit visual light. The second mechanism is advantageous in high luminance, electricity-saving and easiness to form a surface light source structure, but disadvantageous in that the process needs to make an even emission material grow on a cathode or to spread the said material on the cathode, and to implement the process the second mechanism requires a needle-like structure or a carbon nanotube, so that a microstructure with a large aspect ratio (ratio of depth over width) enables the electrons to overcome the work function of the cathode to get rid of the cathode and then travel into a vacuum space. Therefore, the second mechanism is hard to evenly form a cathode structure with large area. In addition, for the second mechanism, the distance between the cathode and the anode for establishing field emission must be accurately controlled, which accordingly requires a strict specification on a spacer structure; plus, the vacuum packaging with the second mechanism is often a worried problem.
Note that the above-mentioned light source apparatuses are targeting the architecture for mono-direction light-emitting. However, such a mono-direction light-emitting apparatus nevertheless has application limitation.